A circuit breaker is a device that can be used to protect an electrical circuit from damage caused by an overload or a short circuit. If a power surge occurs in a circuit protected by the circuit breaker, for example, the breaker will trip. This will cause a breaker that was in the “on” position to flip to the “off” position, and will interrupt the electrical power leading from that breaker. By tripping in this way a circuit breaker can prevent a fire from starting on an overloaded circuit, and can also prevent the destruction of the device that is drawing the electricity or other devices connected to the protected circuit.
A standard circuit breaker has a line and a load. Generally, the line receives incoming electricity, most often from a power company. This is sometimes be referred to as the input into the circuit breaker. The load, sometimes referred to as the output, feeds out of the circuit breaker and connects to the electrical components being fed from the circuit breaker. A circuit breaker may protect an individual component connected directly to the circuit breaker, for example, an air conditioner, or a circuit breaker may protect multiple components, for example, household appliances connected to a power circuit which terminates at electrical outlets.
A circuit breaker can be used as an alternative to a fuse. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. When the power to an area shuts down, an operator can inspect the electrical panel to see which breaker has tripped to the “off” position. The breaker can then be flipped to the “on” position and power will resume again.
In general, a circuit breaker has two contacts located inside of a housing. Typically, the first contact is stationary, and may be connected to either the line or the load. Typically, the second contact is movable with respect to the first contact, such that when the circuit breaker is in the “off”, or tripped position, a gap exists between the first and second contact, and the line is disconnected from the load.
Circuit breakers are usually designed to be operated infrequently. In typical applications circuit breakers will be operated only when tripped by a power spike or other electrical disturbance. Power spikes do not regularly occur during normal operation of typical circuits.
In some applications however, it is desirable to operate circuit breakers more frequently. For example, in the interest of saving electricity it may be beneficial to control the power distribution to an entire floor of a building from one location. This can be done by manually tripping a breaker for the entire floor circuit. It may also be desirable to manually trip the circuit breaker remotely, using a remote control, timer, motion sensor, or the like.
In other applications, it is desirable to operate a circuit breaker remotely for maintenance purposes. For example, an operator may manually trip a circuit breaker to de-energize a protected circuit so that it can be inspected or serviced. However in some circuits, operating the breaker can produce a dangerous arc, creating a safety hazard for the operator. In still other circuits, the circuit breaker may be located in a confined or hazardous environment. In these situations, it is also beneficial to operate the circuit breaker remotely.
Known approaches to remotely controlling circuit breakers include incorporating a mechanism into the circuit breaker which can intentionally trip the circuit breaker mechanism and reset it. Examples of such mechanisms are solenoids or motors used to activate the trip mechanism, and solenoids or motors which are used to reset the circuit breaker by rearming the trip mechanism.
However, using a circuit breaker as a power switch or remote control in this way subjects the breaker to a far greater number of operational cycles than it would otherwise experience in a typical circuit protection application. This can result in an unacceptably premature failure of the circuit breaker. Typical circuit breaker mechanisms are designed to survive only 20,000-30,000 cycles before failure.
In order to increase the number of cycles that such circuit breakers can endure before failure, all of the components of the circuit breaker, including the tripping mechanism and any springs, linkages, escapements, sears, dashpots, bimetal thermal components, or other components that are part of the mechanism must be designed in a more robust way than would otherwise be required. This increases the cost of producing the circuit breaker considerably.
These problems were addressed with great success by the invention disclosed in U.S. patent application Ser. No. 13/598,217 filed on Aug. 29, 2012, which application is also assigned to the assignee of the present application. However, even though the design disclosed therein provides significant advantages over previously known remote operated circuit breaker designs, room for additional features has been discovered.
More specifically, while as discussed in U.S. patent application Ser. No. 13/598,217, it may be desirable to “lock” the breaker in the “remote open” state if DC power to the solenoid is lost when the breaker is in that state for the sake of safety, it has been found that in some applications it may be desirable to enable “manual reset” of the circuit breaker in the event the solenoid loses DC power regardless of the position of the solenoid at the time power is lost. For example, when the breaker is in the “remote open” state and the DC power is lost, the permanent magnet in the solenoid may hold the plunger in that position. If this happens when using the previous design disclosed in U.S. patent application Ser. No. 13/598,217, the breaker will not be able to be manually reset to “closed” if the DC power is not present. While this may be desirable for some applications, it may not be desirable for all applications.
What is desired therefore, is a circuit breaker that can be remotely or manually activated and also that allows for the breaker to be able to be manually reset to the “closed” position even if DC power to the solenoid is lost when the breaker is in the “remote open” state.